Plants and fungi co-operate and trade with each other on a biological ‘underground market’, changing their trading partners if they don’t get a fair deal.

The finding was made by an international team, including Oxford University scientists, examining how plants trade energy-rich carbohydrate they make using photosynthesis for phosphorus fungi collect from the soil. They found that plants use their roots to actively search out fungi to trade with but will attempt to avoid ‘cheating’ fungi which ‘hoard’ phosphorus instead of paying their fair share in return for carbohydrate.

A report of the research is published in this week’s Science.

‘This is one of the first recorded examples of a ‘biological market’ operating in which both partners reward fair trading rather than one partner having the advantage and exploiting the other,’ said Professor Stuart West of Oxford University’s Department of Zoology, an author of the paper. ‘We’ve shown that both plants and fungi can be choosy, ‘playing the market’ and looking for a better trading partner if they aren’t getting a good deal.’

The team used the plant Medicago truncatula, which is related to alfalfa, and then observed its interactions with three different species of fungi; Glomus intraradices, Glomus custos, and Glomus aggregatum, which exhibit different levels of cooperation. They used radioactive tags to track the carbon produced by the plant and the phosphorous harvested by the fungi. The results showed that not only was more carbon supplied to the more cooperative – ‘fairer trading’ – species of fungi but also that more phosphorus was supplied to more cooperative plants.

‘We think that this sort of biological market, reminiscent of a market economy, has arisen because there are so many different individuals either partner could trade with,’ said Professor West. ‘Rather like with human traders, if they are given a chance both plants and fungi will go elsewhere to get a better deal.’